The duplication process of Escherichia coli will be investigated with emphasis on the mechanisms which control the frequency of chromosome replication and cell division. The following projects will be undertaken to investigate the molecular mechanisms involved in initiation of chromosome replication: 1) Identification and analysis of replicative intermediates formed during duplication of oriC-containing plasmids; 2) electron microscopic examination of the structures of oriC-plasmid replicative intermediates; 3) studies on the replication of oriC-plasmids in E. cli B/r dnaA5 and dnaC2 mutants grown at temperatures intermediate between permissive and nonpermissive; and 4) analysis of the synthesis of oriC-binding proteins with respect to initiation and elongation of the E. coli chromosome.